Secondary battery

ABSTRACT

Provided is a secondary battery including an electrode assembly and an electrolyte enclosed in an exterior case. The electrode assembly includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. The secondary battery includes a spacer positioned between the electrode assembly and an exterior case, and the electrode assembly includes current collecting tabs of a positive electrode and a negative electrode each protruding from the same end face. The spacer is positioned between an end face, of the electrode assembly, from which the current collecting tab protrudes and the exterior case, and at least one of the current collecting tabs of the positive electrode or the negative electrode has a bent shape between the electrode assembly and the spacer.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of PCT patent application no.PCT/JP2020/016960, filed on Apr. 17, 2020, which claims priority toJapanese patent application no. JP2019-084574 filed on Apr. 25, 2019,the entire contents of which are being incorporated herein by reference.

BACKGROUND

The present disclosure generally relates to a secondary battery.

The secondary battery can be repeatedly charged and discharged becauseof a so-called storage battery, and is used for various applications.For example, secondary batteries are used in mobile devices such asmobile phones, smartphones, and notebook computers.

The secondary battery generally has a structure in which an electrodeassembly is housed in an exterior case. That is, in the secondarybattery, the electrode body is housed in the exterior case as the case.

SUMMARY

The present disclosure generally relates to a secondary battery.

The inventors of the present application have noticed that there is aproblem to be overcome in the conventional secondary battery, and havefound a need to take measures therefor. Specifically, the inventors ofthe present application have found that there are the followingproblems.

A secondary battery generally has a structure in which an electrodeassembly including a positive electrode, a negative electrode, and aseparator disposed therebetween, and an electrolyte are enclosed in anexterior case. The electrode assembly includes current collecting tabsof a positive electrode and a negative electrode each protruding fromthe same end face of the electrode assembly. In addition, a spacer forinsulation between these members is provided between the electrodeassembly and the exterior case.

In the exemplary embodiment shown in FIG. 10, the current collecting tab6 protrudes from the end face 200′ of the electrode assembly 200. Forinsulation between the electrode assembly 200 and the exterior case 300,a spacer 4 is provided close to the end face 200′. The spacer 4 isprovided with an opening 8 through which the current collecting tab 6passes. The current collecting tab 6 crosses the opening 8 of the spacer4 and is positioned between the spacer 4 and the exterior case 300.

In the secondary battery having such a configuration, when an impact orheat is applied, the electrode assembly 200 may collide with the spacer4 and cause a short circuit.

The present disclosure has been made in view of such problems. That is,a main object of the present disclosure is to provide a secondarybattery more suitable from the viewpoint of preventing a short circuit.

According to an embodiment of the present disclosure, a secondary isprovided. The secondary battery includes an electrode assembly and anelectrolyte enclosed in an exterior case. The electrode assemblyincludes a positive electrode, a negative electrode, and a separatordisposed between the positive electrode and the negative electrode. Thesecondary battery includes a spacer positioned between the electrodeassembly and the exterior case. The electrode assembly includes currentcollecting tabs of a positive electrode and a negative electrode eachprotruding from a same end face of the electrode assembly. The spacer ispositioned between an end face, of the electrode assembly, from whichthe current collecting tabs each protrude and an exterior case. At leastone of the current collecting tabs of the positive electrode or thenegative electrode has a bent shape between the electrode assembly andthe spacer.

The secondary battery according to the present disclosure has a moresuitable structure from the viewpoint of preventing a short circuit.

Specifically, in the secondary battery according to the presentdisclosure, at least one of the current collecting tabs of the positiveelectrode and the negative electrode has a bent shape between theelectrode assembly and the spacer. In other words, the currentcollecting tab having a bent shape is positioned in the space betweenthe electrode assembly and the spacer. Accordingly, when heat and/orimpact is applied to the secondary battery, the current collecting tabfunctions as a cushioning material, and collision of the electrodeassembly and the spacer can be prevented. Therefore, a short circuit inthe electrode assembly can be more suitably prevented.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A and 1B are schematic sectional views (FIG. 1A: non-wound planarlamination type battery, FIG. 1B: wound battery) of an electrodeassembly according to an embodiment of the present disclosure.

FIG. 2 is a schematic perspective developed view of a secondary batteryaccording to an embodiment of the present disclosure.

FIG. 3 is a schematic perspective view of the secondary batteryaccording to an embodiment of the present disclosure.

FIG. 4 is a schematic sectional view of the secondary battery takenalong line a-a′ in FIG. 3.

FIG. 5 is a schematic sectional view of the secondary battery takenalong line b-b′ in FIG. 3.

FIGS. 6A to 6F are schematic diagrams of various aspects of a currentcollecting tab according to an embodiment of the present disclosure.

FIG. 7 is a schematic sectional view of the secondary battery takenalong line c-c′ in FIG. 3.

FIG. 8 is a schematic perspective view for explaining constituentmembers of an electrode assembly constituting the secondary batteryaccording to an embodiment of the present disclosure.

FIGS. 9A and 9B are schematic perspective views for explaining a methodof assembling electrodes constituting the secondary battery according toan embodiment of the present disclosure.

FIG. 10 is a schematic sectional view of a secondary battery accordingto a conventional technique.

DETAILED DESCRIPTION

Hereinafter, a secondary battery according to an embodiment of thepresent disclosure will be described in more detail. Although thedescription will be made with reference to the drawings as necessary,various elements in the drawings are merely schematically andexemplarily illustrated for understanding of the present disclosure, andappearance, dimensional ratios, and the like may be different fromactual ones.

The direction of the “thickness” described directly or indirectly in thepresent specification is based on the lamination direction of theelectrode materials constituting the secondary battery. For example, inthe case of a “secondary battery having a thickness in a plate shape”such as a flat battery, the direction of the “thickness” corresponds tothe plate thickness direction of the secondary battery.

In the present specification, the term “sectional view” is based on avirtual section of an object obtained by cutting along the thicknessdirection of the secondary battery. For example, it is based on asection cut along a face constituted by a thickness direction based on alamination direction of electrode layers constituting the secondarybattery and a longitudinal direction in which the electrode layersextend in a direction in which the electrode terminals are located. Inshort, it is based on the form of the section of the secondary batteryshown in FIG. 4 and the like.

The present disclosure provides a secondary battery. In the presentspecification, the term “secondary battery” refers to a battery that canbe repeatedly charged and discharged. The “Secondary battery” is notexcessively restricted to its name, and may include, for example, anelectrochemical device such as an “electrical storage device”.

A secondary battery according to the present disclosure includes anelectrode assembly having an electrode constituent unit including apositive electrode, a negative electrode, and a separator. FIGS. 1A and1B illustrate the electrode assembly 200. As illustrated, a positiveelectrode 1 and a negative electrode 2 are laminated with a separator 3interposed therebetween to form an electrode constituent unit 100. Theelectrode assembly is configured by laminating at least one or more ofsuch electrode constituent units (see FIG. 1A), or the electrodeassembly is configured by winding the electrode constituent unit (seeFIG. 1B). In the secondary battery, such an electrode assembly togetherwith an electrolyte (for example, a nonaqueous electrolyte) is enclosedin an exterior case.

The positive electrode includes at least a positive electrode materiallayer and a positive electrode current collector (for example, apositive electrode current collector in a layer form). In the positiveelectrode, a positive electrode material layer is provided on at leastone face of the positive electrode current collector, and the positiveelectrode material layer contains a positive electrode active substanceas an electrode active substance. For example, in each of the pluralityof positive electrodes in the electrode assembly, the positive electrodematerial layer may be provided on both faces of the positive electrodecurrent collector, or the positive electrode material layer may beprovided only on one face of the positive electrode current collector.From the viewpoint of further increasing the capacitance of thesecondary battery, the positive electrode preferably includes thepositive electrode material layer on both faces of the positiveelectrode current collector.

The negative electrode includes at least a negative electrode materiallayer and a negative electrode current collector (for example, anegative electrode current collector in a layer form). In the negativeelectrode, a negative electrode material layer is provided on at leastone face of a negative electrode current collector, and the negativeelectrode material layer contains a negative electrode active substanceas an electrode active substance. For example, in each of the pluralityof negative electrodes in the electrode assembly, the negative electrodematerial layer may be provided on both faces of the negative electrodecurrent collector, or the negative electrode material layer may beprovided only on one face of the negative electrode current collector.From the viewpoint of further increasing the capacitance of thesecondary battery, the negative electrode preferably includes thenegative electrode material layer on both faces of the negativeelectrode current collector.

The electrode active substances contained in the positive electrode andthe negative electrode, that is, the positive electrode active substanceand the negative electrode active substance are substances directlyinvolved in electron transfer in the secondary battery, and are mainsubstances of positive and negative electrodes responsible for chargeand discharge, that is, the cell reaction. More specifically, ions aregenerated in the electrolyte due to “the positive electrode activesubstance contained in the positive electrode material layer” and “thenegative electrode active substance contained in the negative electrodematerial layer”, and such ions are transferred between the positiveelectrode and the negative electrode to transfer electrons, resulting incharging and discharging. It is preferable that the positive electrodematerial layer and the negative electrode material layer be layerscapable of absorbing and releasing lithium ions, in particular. That is,the battery is preferably a nonaqueous electrolyte secondary battery inwhich lithium ions move between the positive electrode and the negativeelectrode with the nonaqueous electrolyte interposed therebetween tocharge and discharge the battery. When lithium ions are involved incharging and discharging, the secondary battery according to the presentdisclosure corresponds to a so-called lithium ion battery, and thepositive electrode and the negative electrode have a layer capable ofabsorbing and releasing lithium ions.

The positive electrode active substance of the positive electrodematerial layer, which comprises, for example, a granular material,preferably includes a binder in the positive electrode material layerfor more sufficient contact between grains and shape retention.Furthermore, a conductive auxiliary agent may be contained in thepositive electrode material layer in order to facilitate transmission ofelectrons for promoting the cell reaction. Similarly, the negativeelectrode active substance of the negative electrode material layer,which comprises, for example, a granular material, preferably includes abinder for sufficient contact between grains and shape retention, and aconductive auxiliary agent for smooth transfer of electrons promoting acell reaction may be included in the negative electrode material layer.As described above, since the plurality of components is contained, thepositive electrode material layer and the negative electrode materiallayer can also be referred to as “positive electrode mixture materiallayer” and “negative electrode mixture material layer”, respectively.

It is preferable that the positive electrode active substance be asubstance contributing to absorbing and releasing of lithium ions. Inthis respect, it is preferable that the positive electrode activesubstance be, for example, a lithium-containing composite oxide. Morespecifically, the positive electrode active substance may be a lithiumtransition metal composite oxide containing lithium and at least onetransition metal selected from the group consisting of cobalt, nickel,manganese, and iron. That is, in the positive electrode material layerof the secondary battery according to the embodiment, such a lithiumtransition metal composite oxide is preferably included as a positiveelectrode active substance. For example, the positive electrode activesubstance is lithium cobalt oxide, lithium nickel oxide, lithiummanganate, lithium iron phosphate, or a material in which some of theirtransition metals are replaced with another metal. Although such apositive electrode active substance may be included as a singlematerial, two or more materials may be contained in combination.

The binder that can be contained in the positive electrode materiallayer is not particularly limited, but examples thereof may include atleast one selected from the group consisting of polyvinylidene fluoride,vinylidene fluoride-hexafluoropropylene copolymer, vinylidenefluoride-tetrafluoroethylene copolymer, polytetrafluoroethylene and thelike. The conductive auxiliary agent which can be contained in thepositive electrode material layer is not particularly limited, butexamples thereof may include at least one selected from the groupconsisting of carbon black such as thermal black, furnace black, channelblack, ketjen black and acetylene black, carbon fiber such as graphite,carbon nanotube and vapor phase growth carbon fiber, metal powder suchas copper, nickel, aluminum and silver, polyphenylene derivative and thelike. In an exemplary embodiment, the binder of the positive electrodematerial layer is polyvinylidene fluoride, and in another exemplaryembodiment, the conductive auxiliary agent of the positive electrodematerial layer is carbon black. In a further exemplary embodiment, thebinder and the conductive auxiliary agent of the positive electrodematerial layer are a combination of polyvinylidene fluoride and carbonblack.

The thickness dimension of the positive electrode material layer is notparticularly limited, but is preferably 1 μm or more and 300 μm or less,for example, 5 μm or more and 200 μm or less. The thickness dimension ofthe positive electrode material layer is the thickness inside thesecondary battery, and an average value of measured values at any 10points is used.

The negative electrode active substance is preferably a substance thatcontributes to absorbing and releasing of lithium ions. In this respect,it is preferable that the negative electrode active substance be, forexample, various carbon materials, oxides or lithium alloys.

Examples of various carbon materials of the negative electrode activesubstance include graphite (for example, natural graphite and/orartificial graphite), hard carbon, soft carbon, and/or diamond-likecarbon. Specifically, graphite is preferable because it has highelectron conductivity and excellent adhesion to a negative electrodecurrent collector and the like. Examples of the oxide of the negativeelectrode active substance may include at least one selected from thegroup consisting of silicon oxide, tin oxide, indium oxide, zinc oxide,lithium oxide and the like. The lithium alloy of the negative electrodeactive substance may be any metal that can be alloyed with lithium andexamples thereof may include a binary, ternary or higher alloy of ametal such as Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn,and La, and lithium. Such an oxide may be amorphous as its structuralform. This is because degradation due to nonuniformity such as grainboundaries or defects hardly occurs. In an exemplary embodiment, thenegative electrode active substance of the negative electrode materiallayer is artificial graphite.

The binder that can be contained in the negative electrode materiallayer is not particularly limited, but examples thereof may include atleast one selected from the group consisting of styrene butadienerubber, polyacrylic acid, polyvinylidene fluoride, polyimide-based resinand polyamideimide-based resin. In a more preferred embodiment, thebinder contained in the negative electrode material layer is styrenebutadiene rubber. The conductive auxiliary agent which can be containedin the negative electrode material layer is not particularly limited,but examples thereof may include at least one selected from the groupconsisting of carbon black such as thermal black, furnace black, channelblack, ketjen black and acetylene black, carbon fiber such as graphite,carbon nanotube and vapor phase growth carbon fiber, metal powder suchas copper, nickel, aluminum and silver, polyphenylene derivative and thelike. The negative electrode material layer may contain a componentattributable to the thickener component (for example, carboxymethylcellulose) used at the time of manufacturing the battery.

In an exemplary embodiment, the negative electrode active substance andthe binder in the negative electrode material layer are a combination ofartificial graphite and styrene butadiene rubber.

The thickness dimension of the negative electrode material layer is notparticularly limited, but is preferably 1 μm or more and 300 μm or less,for example, 5 μm or more and 200 μm or less. The thickness dimension ofthe negative electrode material layer is the thickness inside thesecondary battery, and an average value of measured values at any 10points is used.

The positive electrode current collector and the negative electrodecurrent collector used for the positive electrode and the negativeelectrode are members that contribute to the collection and supply ofelectrons generated in the active substance due to the cell reaction.Such a current collector may be a sheet-like metal member and may have aporous or perforated form. For example, the current collector is a metalfoil, a punching metal, a net, an expanded metal or the like. Thepositive electrode current collector used for the positive electrodepreferably comprises a metal foil containing at least one selected fromthe group consisting of aluminum, stainless steel, nickel and the like,and may be, for example, an aluminum foil. On the other hand, thenegative electrode current collector used for the negative electrodepreferably comprises a metal foil containing at least one selected fromthe group consisting of copper, stainless steel, nickel and the like,and may be, for example, a copper foil.

The separator is a member provided from the viewpoint of prevention ofshort circuit by contact of the positive and negative electrodes,retention of the electrolyte and the like. In other words, it can besaid that the separator is a member that passes ions while preventingelectronic contact between the positive electrode and the negativeelectrode. Preferably, the separator is a porous or microporousinsulating member and has a film form due to its small thickness.Although it is merely an example, a microporous membrane made ofpolyolefin may be used as a separator. In this regard, the microporousmembrane used as a separator may be, for example, a polyolefincontaining only polyethylene (PE) or polypropylene (PP). Furthermore,the separator may be a laminate composed of a “microporous membrane madeof PE” and a “microporous membrane made of PP”. The surface of theseparator may be covered with an inorganic grain coat layer and/or anadhesive layer or the like. The surface of the separator may haveadhesion.

The thickness dimension of the separator is not particularly limited,but is preferably 1 μm or more and 100 μm or less, for example, 5 μm ormore and 20 μm or less. The thickness dimension of the separator is thethickness inside the secondary battery (particularly, the thicknessbetween the positive electrode and the negative electrode), and anaverage value of measured values at any 10 points is used.

The thickness dimension of the separator is the thickness inside thesecondary battery (particularly, the thickness between the positiveelectrode and the negative electrode), and an average value of measuredvalues at any 10 points may be used. The electrolyte assists themovement of the metal ions released from the electrodes (positiveelectrode/negative electrode). The electrolyte may be a “nonaqueous”electrolyte such as an organic electrolyte and an organic solvent, ormay be an “aqueous” electrolyte containing water. In an exemplaryembodiment, the secondary battery according to the present disclosure isa nonaqueous electrolyte secondary battery using an electrolytecontaining a “nonaqueous” solvent and a solute as an electrolyte.

It is preferable to include at least carbonate as a specific solvent forthe nonaqueous electrolyte. Such carbonate may be cyclic carbonatesand/or chain carbonates. Although not particularly limited, examples ofthe cyclic carbonates may include at least one selected from the groupconsisting of propylene carbonate (PC), ethylene carbonate (EC),butylene carbonate (BC) and vinylene carbonate (VC). Examples of thechain carbonates may include at least one selected from the groupconsisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC) and dipropyl carbonate (DPC). In one exemplaryembodiment of the present disclosure, a combination of cyclic carbonatesand chain carbonates is used as the nonaqueous electrolyte, and, forexample, a mixture of ethylene carbonate and diethyl carbonate is used.As a specific nonaqueous electrolyte solute, for example, Li salts suchas LiPF6 and LiBF4 are preferably used.

As the current collecting tab, any current collecting tab used in thefield of secondary battery can be used. The current collecting tab maybe composed of a material for which electron transfer can be achieved,and is usually composed of a conductive material such as silver, gold,copper, iron, tin, platinum, aluminum, nickel, and/or stainless steel.The form of the current collecting tab is not particularly limited, andmay be, for example, a linear shape or a plate shape. The currentcollecting tabs of the positive electrode and the negative electrode(hereinafter also collectively referred to as “current collecting tabsof positive and negative electrodes”) may protrude from any face of theelectrode assembly. The current collecting tabs of the positive andnegative electrodes may protrude from different faces of the electrodeassembly, or may protrude from the same face. From the viewpoint ofmaking the secondary battery compact, it is preferable that the currentcollecting tabs of the positive and negative electrodes protrude fromthe same face. That is, the positive electrode current collecting taband the negative electrode current collecting tab may extend so as toprotrude from the same end face (that is, the same side face) of theelectrode assembly.

The exterior case is usually a hard case, and may be composed of twomembers such as a main body and a lid. For example, in a case where theexterior case includes a main body and a lid, the main body and the lidare sealed after the electrode assembly, the electrolyte, the currentcollecting tab, the electrode terminal as desired, and the like arehoused. The method of sealing the exterior case is not particularlylimited, and examples thereof include a laser irradiation method.

Any material that can constitute a hard case exterior case in the fieldof secondary batteries can be used as the material constituting the mainbody and the lid of the exterior case. Such a material may be aconductive material for which electron transfer may be achieved or aninsulating material for which electron transfer may not be achieved. Thematerial of the exterior case is preferably a conductive material fromthe viewpoint of taking out the electrode.

Examples of the conductive material include conductive materials such assilver, gold, copper, iron, tin, platinum, aluminum, nickel, and/orstainless steel. Examples of the insulating material include insulatingpolymer materials such as polyester (for example, polyethyleneterephthalate), polyimide, polyamide, polyamideimide, and/or polyolefin(for example, polyethylene and/or polypropylene).

From the viewpoint of the above-described conductivity and rigidity,both the main body and the lid may be made of stainless steel. Asdefined in “JIS G0203 Glossary of terms used in iron and steel”,stainless steel is chromium or alloy steel containing chromium orchromium and nickel, and generally refers to steel having a chromiumcontent of about 10.5% or more of the whole. Examples of such stainlesssteel include martensitic stainless steel, ferritic stainless steel,austenitic stainless steel, austenitic ferritic stainless steel and/orprecipitation hardening stainless steel.

The dimensions of the main body and the lid of the exterior case aremainly determined according to the dimensions of the electrode assembly.For example, it is preferable that the exterior case has such adimension that movement of the electrode assembly in the exterior caseis prevented when the electrode assembly is housed. By preventing themovement of the electrode assembly, damage to the electrode assembly dueto impact or the like can be prevented, and the safety of the secondarybattery can be improved.

The exterior case may be a flexible case such as a pouch made of alaminated film. Examples of the laminated film may have a configurationin which at least a metal layer (for example, aluminum or the like) andan adhesive layer (for example, polypropylene and/or polyethylene, etc.)are laminated, and a configuration in which a protective layer (forexample, nylon and/or polyamide, etc.) is additionally laminated.

The thickness dimension (that is, the thickness dimension) of theexterior case is not particularly limited, but is preferably 10 μm ormore and 200 μm or less, for example, 50 μm or more and 100 μm or less.As the thickness dimension of the exterior case, an average value ofmeasured values at any 10 points is used.

The secondary battery is generally provided with an electrode terminal.Such an electrode terminal may be provided on at least one face of theexterior case. For example, the electrode terminal of the positiveelectrode and the electrode terminal of the negative electrode may beprovided away from each other on the same face of the exterior case.Alternatively, the electrode terminal of the positive electrode and theelectrode terminal of the negative electrode may be provided ondifferent faces of the exterior case. From the viewpoint of making thesecondary battery compact, the electrode terminal of the positiveelectrode and the electrode terminal of the negative electrode mayprotrude from the same face. Specifically, the electrode terminals ofthe positive electrode and the negative electrode may protrude from theside face of the exterior case so as to protrude in a directionperpendicular to the direction in which the electrode layers arelaminated.

The electrode terminal preferably comprises a material having highconductivity. The material of the electrode terminal is not particularlylimited, but may be at least one selected from the group consisting ofsilver, gold, copper, iron, tin, platinum, aluminum, nickel, andstainless steel.

The electrode terminal may be composed of a single material or may becomposed of a plurality of materials. An electrode terminal(hereinafter, also referred to as an “electrode terminal structure”)composed of a plurality of materials includes a rivet portion, an innerterminal, and a gasket portion.

The rivet portion and the inner terminal may be composed of a materialcapable of achieving movement of electrons. For example, the rivetportion and the inner terminal are each composed of a conductivematerial such as silver, gold, copper, iron, tin, platinum, aluminum,nickel, and/or stainless steel. The gasket portion may be composed of aninsulating material. For example, the gasket portion is composed of aninsulating polymer material such as polyester (for example, polyethyleneterephthalate), polyimide, polyamide, polyamideimide, and/or polyolefin(for example, polyethylene and/or polypropylene).

Each of the current collecting tabs of the positive and negativeelectrodes is electrically connected to the electrode terminal or theelectrode terminal structure, and is electrically led out to the outsidewith the electrode terminal or the electrode terminal structureinterposed therebetween.

Although the electrode terminal structure is not particularly limited,for example, the electrode terminal structure may be fitted and insertedinto the through hole of the exterior case. The electrode terminalstructure may include a conductive rivet portion for mainly leading theelectrode to the outside, an outer gasket portion for preventing leakageof the electrolyte while ensuring electrical insulation between therivet portion and the exterior case, an inner terminal for ensuringelectrical connection between the rivet portion and the currentcollecting tab, and an inner gasket portion for preventing leakage ofthe electrolyte while ensuring electrical insulation between the innerterminal and the exterior case.

The current collecting tabs of the positive and negative electrodes maybe connected to an electrode terminal or an electrode terminalstructure. In addition, the current collecting tabs of the positive andnegative electrodes may be electrically connected to the exterior caseand electrically led out to the outside with the exterior caseinterposed therebetween. For example, when the exterior case is aconductive hard case type exterior case, the current collecting tab maybe in contact with and electrically connected to the inside of theexterior case, and may be led out to the outside with the exterior caseinterposed therebetween. In other words, the exterior case may beconnected to the current collecting tab to assume a charge of thepositive electrode or the negative electrode, and the current collectingtab may be electrically led out to the outside from the electrodeterminal provided on the exterior case.

From the viewpoint of compactness and voltage balancing of the secondarybattery, it is preferable that the current collecting tab of one of thepositive and negative electrodes is electrically connected to theelectrode terminal structure, and the current collecting tab of theother of the positive and negative electrodes is electrically connectedto the inside of the conductive hard case type exterior case.

Any spacer used in the field of secondary battery can be used as thespacer. The spacer is not particularly limited as long as it prevents,for example, electronic contact between the electrode assembly(particularly the electrode) and the exterior case (particularly theelectrode terminal). Therefore, the spacer can also be referred to as aninsulating member that prevents electronic contact between the electrodeassembly and the exterior case (particularly, the electrode terminalthereof). The spacer may have, for example, a plate shape as a whole.Examples of the material constituting the spacer include polymermaterials such as polyolefin (for example, polyethylene and/orpolypropylene, etc.), polystyrene, polyester (for example, polyethyleneterephthalate and/or polybutylene terephthalate), polyvinyl chloride,acrylic polymer (for example, polymethyl methacrylate or the like)and/or polycarbonate, and various insulating materials such as rubbermaterials such as nitrile rubber, urethane rubber, fluororubber and/orsilicone rubber. The spacer may have any form as long as contact betweenthe electrode assembly and the exterior case can be prevented. Forexample, the spacer may have a form of a film, a sheet, a board, or afabric (for example, a nonwoven fabric).

A secondary battery according to the present disclosure is a batteryincluding an electrode assembly and an exterior case housing theelectrode assembly, and is characterized in terms of a form of a currentcollecting tab protruding from the electrode assembly and a positionalrelationship between members around the current collecting tab.

Specifically, in the secondary battery according to the presentdisclosure, at least one of the current collecting tabs of the positiveand the negative electrodes has a bent shape between the electrodeassembly and the spacer. That is, the electrode assembly and the spacerare away from each other, and at least one of the current collectingtabs has a bent shape in the separation space. It can also be said thatat least one of the current collecting tabs of the positive and negativeelectrodes extends in a bent shape in a local space formed between theelectrode assembly and the spacer. In the illustrated exemplaryembodiment, the secondary battery includes the spacer 4 positionedbetween the electrode assembly 200 and the exterior case 300 inside theexterior case 300 (310) (see FIG. 2). The spacer 4 is, for example, aplate-like spacer, and such a spacer 4 is provided so as to partition aspace between one side face (Specifically, an “end face” describedbelow) of the electrode assembly 200 and the exterior case 300. The mainface of the spacer 4 may have a size that can substantially cover oneside face of the electrode assembly 200. For example, as can be seenfrom FIG. 2, the main face of the plate-shaped spacer 4 may havesubstantially the same size as the size of the end face of one side faceof the electrode assembly 200 as a whole.

Such a spacer is provided for the end face 200′ including an outwardlyprotruding current collecting tab. More specifically, the secondarybattery includes the spacer 4 positioned between the end face 200′, ofthe electrode assembly 200, from which the current collecting tabprotrudes and the exterior case 300 (see FIG. 4). The end face 200′ ofthe electrode assembly 200 and the spacer 4 are away from each other. Ascan be seen from the illustrated aspect, the spacer 4 is provided innon-contact with or away from the separator extension portion extendingoutside the positive electrode and the negative electrode. Here, thecurrent collecting tab 6 (that is, the positive electrode currentcollecting tab 61 and/or the negative electrode current collecting tab62) having a bent shape is positioned between the electrode assembly 200and the spacer 4 (see FIGS. 4 and 5). That is, in sectional view, thecurrent collecting tab 6 extends so as to meander due to the bent shapein the separation space between the electrode assembly and the spacer.When the current collecting tab 6 has the bent shape between theelectrode assembly 200 and the spacer 4 as described above, the currentcollecting tab 6 functions as a cushioning material (for example, like aspring) when a fluctuation in impact or heat occurs in the secondarybattery 400, and it is possible to prevent the collision between theelectrode assembly 200 and the spacer 4. More simply, the currentcollecting tab 6 can absorb an impact that may occur, for example,between the electrode assembly 200 and the spacer 4. Therefore, a shortcircuit in the electrode assembly 200 can be more suitably prevented.

In a broad sense, the “bent shape” in the present disclosure refers to aform of a current collecting tab that greatly bends so as to form aconvex shape in sectional view. In a narrow sense, the “bent shape”refers to a form in which a current collecting tab protruding from theelectrode assembly is bent and extended so as to be folded back insectional view. In the exemplary embodiment shown in FIG. 4, when viewedfrom K₃ as a starting point, the current collecting tab 6 goes to aspacer 4 from the electrode assembly 200, and then is bent toward theelectrode assembly 200 from the spacer 4 with the portion K₁ having thebent shape as a boundary. In the exemplary embodiment shown in FIG. 4,the current collecting tab 6 has a portion K₂ having a bent shape bentfrom the electrode assembly 200 toward the spacer 4. As can be seen fromsuch an exemplary embodiment, the current collecting tab protruding fromthe electrode assembly extends so as to meander in the separation spacebetween the electrode assembly and the spacer.

The “bent shape” in the present disclosure can include a bent shaperepresented by a bowed shape and/or a folded shape. As indicated by K₁and K₂ in FIG. 4, the term “bowed shape” means bending in a baylike (orarch) shape (that is, bending in a substantially curved manner) insectional view, which results in rounded bending and also includesflexure. The “folded shape” means bending with an acute angle (that is,bending substantially linearly) in sectional view. From the viewpoint ofimproving impact absorbability, the “bent shape” preferably has a bowedshape. That is, the bent shape of the current collecting tab may be abowed shape bent in an arch shape, so that the current collecting tabcan more suitably absorb an impact that may occur between the electrodeassembly and the spacer. In the exemplary embodiment illustrated in FIG.4, the bent shapes of the portions K₁ and K₂ each having the bent shapeare bowed.

As can be seen from the illustrated aspect, the “bent shape” in thepresent disclosure can also be referred to as a “folded shape”, a“substantially U-shaped (or substantially V-shaped) shape”, a “curvedshape having a maximum point”, a “shape bent with an acute angle”, orthe like.

The current collecting tab 6 may have at least one bent shape in the gapbetween the electrode assembly 200 and the spacer 4. Preferably, thecurrent collecting tabs 6 has a plurality of (for example, two) bentshapes (see FIGS. 4 and 5). Since the current collecting tab 6 has aplurality of bent shapes, the elasticity (for example, springelasticity) of the current collecting tab 6 can be further improved, andan impact that can be generated between the electrode assembly 200 andthe spacer 4 can be further absorbed. From the viewpoint of making thesecondary battery compact, the number of bent shapes of the currentcollecting tabs 6 is preferably 5 or less (that is, the positiveelectrode current collecting tab or the negative electrode currentcollecting tab preferably has 2 or more and 5 or less bent portions in agap space between the electrode assembly 200 and the spacer 4).

For example, in sectional view of the secondary battery 400, the currentcollecting tab 6 may have a portion K₀ having a bent shape so as to forma convex shape in the thickness direction (see FIG. 6A). In addition,the current collecting tab 6 may protrude from the electrode at theoutermost layer of the electrode assembly 200 (see FIG. 6A). Forexample, the current collecting tab 6 may protrude outward from theoutermost layer of the electrode assembly 200 in a direction orthogonalto the lamination direction of the assembly. Furthermore, it mayprotrude from the electrode at the inner layer of the electrode assembly200 (see FIG. 6B). That is, the current collecting tab 6 may protrudeoutward from the electrode at the non-outermost layer that is not theoutermost layer in the electrode assembly 200. When the currentcollecting tab 6 protrudes from the electrode at the inner layer of theelectrode assembly 200, the current collecting tab 6 may have threeportions (that is, K₀, K₁, and K₂) each having the bent shape (see FIG.6C). The electrode assembly 200 may be a planar lamination typeelectrode assembly, and in this case, the sub current collecting tabprotruding from each electrode may be bound to form the currentcollecting tab 6 (see FIG. 6D). When such a planar lamination typeelectrode assembly 200 is used (see FIG. 1A), the current collecting tab6 may be provided separately from the tab electrically connecting theelectrodes in each of the positive electrode and the negative electrode.

At least one of the current collecting tabs of the positive and negativeelectrodes may have a bent shape between the electrode assembly and thespacer, and it is preferable that both the current collecting tabs ofthe positive and negative electrodes each have a bent shape. Since boththe current collecting tabs of the positive and negative electrodes eachhave a bent shape, both the current collecting tabs can have elasticity.In addition, it is possible to form an impact absorbing region atdifferent positions between the electrode assembly and the spacer. As aresult, it is possible to further absorb an impact that may occurbetween the electrode assembly and the spacer. Furthermore, when animpact or heat is applied to the secondary battery, it is possible tomore suitably prevent the electrode assembly and the spacer from moving(particularly, the electrode assembly rotates in the circumferentialdirection in plan view in the exterior case).

In the illustrated exemplary embodiment, the positive electrode currentcollecting tab 61 has a bent shape between the electrode assembly 200and the spacer 4 (see FIG. 4). In addition, the negative electrodecurrent collecting tab 62 has a bent shape between the electrodeassembly 200 and the spacer 4 (see FIG. 5). That is, both the positiveelectrode current collecting tab 61 and the negative electrode currentcollecting tab 62 each have a bent shape in the “separation space” inwhich the same spacer is involved. As a result, it is possible to moreeffectively absorb an impact or the like that may occur between theelectrode assembly 200 and the spacer 4 while taking into account thecompactness of the secondary battery.

In an embodiment, the portion having the bent shape of the currentcollecting tab is in contact with the spacer. That is, the convexportion of the current collecting tab is in contact with the main faceof the spacer in sectional view. Since the portion having the bent shapeof the current collecting tab is in contact with the spacer, it is easyto more effectively absorb an impact or the like that may occur betweenthe electrode assembly 200 and the spacer 4. In the exemplary embodimentshown in FIG. 4, the current collecting tab 6 has the portion K₁ havingthe bent shape. Here, the portion K₁ having the bent shape is in contactwith the spacer 4.

In the secondary battery of the present disclosure, the currentcollecting tab may be in contact with the spacer and may also be incontact with the separator between the electrode assembly and thespacer. That is, for example, as illustrated in FIG. 4, the currentcollecting tab protruding laterally from the electrode assembly is incontact with both the spacer and the separator while meandering due tothe bent shape. This makes it easy to absorb an impact or the like thatmay occur between the electrode assembly 200 and the spacer 4 whiletaking into consideration the compactness of the secondary battery. In apreferred aspect, at least two portions each having the bent shape ofthe current collecting tab are provided, one bent portion of the currentcollecting tab is in contact with the spacer, and the other bent portionof the current collecting tab is in contact with the separator. That is,each or any one of the positive electrode current collecting tab and thenegative electrode current collecting tab extends so as to meander dueto the bent shape, and one of at least two bent portions forming themeander is in contact with the spacer and the other is in contact withthe separator. Since the current collecting tabs are in contact with thespacer and the separator by the independent bent portions in thismanner, it is possible to more effectively absorb an impact or the likewhich may be generated between the electrode assembly and the spacerwhile making the secondary battery compact.

In an embodiment, the electrode assembly has a separator extensionportion in which the separator extends to the outside of the positiveelectrode and the negative electrode at the end face from which thecurrent collecting tab protrudes, and the portion having the bent shapeof the current collecting tab is in contact with the separator extensionportion. The separator extension portion extends outside the positiveelectrode layer and the negative electrode layer particularly in adirection orthogonal to the lamination direction of the electrodeassembly. It can be said that a portion where the separator extendsbeyond the end portions of the electrode layers of the positiveelectrode layer and the negative electrode layer corresponds to theseparator extension portion. In the exemplary embodiment shown in FIG.4, the electrode assembly 200 has a separator extension portion 30 inwhich the separator 3 extends so as to protrude from the positiveelectrode 1 and the negative electrode 2 at the end face 200′ from whichthe current collecting tab 6 protrudes. Here, the portion K₂ having thebent shape of the current collecting tab 6 is in contact with theseparator extension portion 30. As shown in FIG. 4, the folded portionof portions each having the bent shape may be in contact with theseparator extension portion 30.

With the above-described configuration, the portion K₁ and/or K₂ eachhaving a bent shape serves as a fulcrum, and the elasticity of thecurrent collecting tab 6 can be improved. With such a configuration, itis possible to further absorb an impact which may be generated betweenthe electrode assembly 200 and the spacer 4. The separator extensionportion 30 may have a structure in which the plurality of separators 3converges with each other (see FIGS. 4, 5 and 6A to D). Alternatively,the separator extension portion 30 may not have such converging (seeFIG. 6E), and the end of the separator extension portion 30 may be incontact with the bent portion of the current collecting tab. In theaspect shown in FIG. 6E, the current collecting tab protruding from theelectrode assembly extends so as to meander in the separation spacebetween the electrode assembly (particularly, the electrode assemblywithout the separator) and the spacer.

In a more preferred embodiment, the portions K₁ and K₂ each having thebent shape of the current collecting tab 6 are in contact with thespacer 4 and the separator extension portion 30, respectively (see FIG.4 and the like). With such a configuration, each fulcrum can be formedsuch that the current collecting tab 6 is interposed between theelectrode assembly 200 and the spacer 4. Thereby, the elasticity of thecurrent collecting tab 6 can be particularly improved, and an impactthat can be generated between the electrode assembly 200 and the spacer4 can be further absorbed.

The spacer may have an opening or a recess for the current collectingtab. Accordingly, the current collecting tab 6 can be extended from oneside (that is, the electrode assembly 200 side) to the other side (thatis, the exterior case 300 side) of the spacer 4 (see FIG. 4). That is,the current collecting tab 6 can extend so as to straddle the spacer 4with such an opening or a recess interposed therebetween. As shown insectional view of FIG. 4, the current collecting tab may extend in ameandering manner while being in contact with the separator of theelectrode assembly and the spacer in the separation space between theelectrode assembly and the spacer, and may extend further outward beyondthe spacer. Such a form contributes to compactness of the secondarybattery and/or contributes to prevention of interference between thecurrent collecting tab and other battery constituent members.

In an embodiment, the current collecting tab extends from a face, of thespacer, toward the electrode assembly to a face, of the spacer, towardthe exterior case so as to straddle opposing faces of the main face ofthe spacer. In the exemplary embodiment shown in FIG. 4, the currentcollecting tab 6 extends from the face toward the electrode assembly 200to the face toward the exterior case 300 so as to straddle the main faceof the spacer 4. For example, the current collecting tab may extend soas to be in contact with the opposing sides of the main face of thespacer 4. Here, “extending so as to straddle the opposing faces of themain face of the spacer” means that the tab extends on the opposingsides of the main face of the spacer 4 so as to reach at least ¼ or moreof the sectional view dimension of the spacer 4 in sectional view of thesecondary battery 400. With such a configuration, the current collectingtab and the spacer can be more suitably interfered with each other.Therefore, it is easy to prevent the spacer 4 from moving, and it iseasy to reduce the impact that may occur between the electrode assembly200 and the spacer 4.

In an embodiment, the electrode assembly 200 is a wound electrodeassembly in which a positive electrode, a negative electrode, and aseparator are wound (see FIG. 1B). Since the electrode assembly 200 hasa wound configuration, it can have a structure in which the separatorextension portion 30 converges toward the winding axis (see FIG. 4 andthe like). Further, by laminating the separators 3 with a hollow portion(for example, an air layer) interposed therebetween, the separatorextension portion 30 can easily have a cushioning property. This alsomakes it easy for the separator extension portion 30 to absorb an impactthat may occur between the electrode assembly 200 and the spacer 4.

In an embodiment, at least part of the separator extension portion 30has a bent shape convex toward the outer periphery of the winding (seeFIG. 4 and the like). More specifically, at least part of the separatorextension portion 30 has a portion K₃ having the bent shape convextoward the outer periphery of the winding. As a result, more hollowportions can be interposed between the separators 3, and the separatorextension portion 30 can have a particularly cushioning property. Here,the “bent shape protruding toward the outer periphery” refers to a bentshape convex from the inner periphery toward the outer periphery in thewinding direction in sectional view.

In an embodiment, the electrode assembly 200 has a convergence portion30B where the separator extension portion 30 converges, and the portionK₂ having the bent shape of the current collecting tab 6 is in contactwith the convergence portion 30B (see FIG. 6F). Here, the “convergenceportion 30B” is a portion where the separator 3 converges toward thewinding axis of the electrode assembly 200, and is positioned at thecentral portion of the end face 200′ of the electrode assembly. Sincethe fulcrum is formed at the central portion of the electrode assemblyby the portion having the bent shape being in contact with theconvergence portion, the structural stability between the batteryconstituent members can be further enhanced.

In an embodiment, an insulating material is provided at least on aportion having the bent shape of the current collecting tab. With such aconfiguration, the elasticity of the current collecting tab is improvedby the elasticity of the insulating material, and the impact can befurther absorbed. In addition, insulation between the current collectingtab, the electrode assembly, and the exterior case can be furtherenhanced. For example, in sectional view, a member of an insulatingmaterial (in particular, a member of an insulating material forming alayer with the tab) may be provided on an inner portion and/or an outerportion of the bent portion of the current collecting tab. Examples ofthe insulating material include insulating polymer materials such aspolyester (for example, polyethylene terephthalate), polyimide,polyamide, polyamideimide, and/or polyolefin (for example, polyethyleneand/or polypropylene). From the viewpoint of providing a more intendedbent shape, the insulating material preferably comprises polypropylene.

In an embodiment, one face of the main face of the spacer is in contactwith the electrode terminal structure of the exterior case. Morespecifically, in sectional view of the secondary battery 400, theelectrode terminal structure 5′ is provided on the exterior case 300,and the spacer 4 is in contact with the rivet portion 50 of theelectrode terminal structure 5′ (or attached to a rivet portion 50) (seeFIG. 7). With such a configuration, it is possible to provide a space inwhich the current collecting tab can extend between the spacer 4 and theexterior case 300 while preventing the positional deviation between thespacer 4 and the exterior case 300.

In a more preferred embodiment, the spacer 4 may include an adhesivelayer, and the adhesive layer and the exterior case 300 may be incontact with each other (see FIG. 7). When the spacer 4 is in contactwith the exterior case 300 with the adhesive layer interposedtherebetween, the positional deviation between the spacer 4 and theexterior case 300 can be particularly prevented.

In an embodiment, the exterior case further includes an electrodeterminal structure of any one of the positive electrode terminal and thenegative electrode terminal, and part of each of the current collectingtabs is positioned between the spacer and the electrode terminalstructure. In the illustrated exemplary embodiment, the adhesive layerprovided on the main face of the spacer 4 toward the exterior case 300is in contact with the rivet portion 50 of the electrode terminalstructure 5′ (see FIG. 7). One end, of the positive electrode currentcollecting tab 61, extending toward the exterior case 300 is attached tothe inner terminal 51 of the electrode terminal structure 5′ (that is,the positive electrode terminal 5 ₁) (see FIGS. 4 and 7). Similarly, oneend, of the negative electrode current collecting tab 62, extendingtoward the exterior case 300 is attached to a position, of the inside ofthe exterior case 300, corresponding to the negative electrode terminal52 (see FIG. 5). With such a configuration, the spacer and the currentcollecting tab are each fixed to the exterior case, and the positionaldeviation between the spacer and the current collecting tab can befurther prevented.

In an embodiment, the length dimension of the current collecting tab is1 mm or more and 30 mm or less. The “length dimension” herein refers toa length when the current collecting tab is straightly extended. Whenthe length dimension is 1 mm or more, the bent shape (specifically, aplurality of bent shapes) can be more easily formed. Accordingly, thecurrent collecting tab can have more excellent elasticity. When thelength dimension is 30 mm or less, the secondary battery can be mademore compact. In addition, the handling property of the currentcollecting tab can be further improved. The length dimension of thecurrent collecting tab is preferably 2 mm or more and 20 mm or less, andis, for example, 5 mm or more and 10 mm or less.

In an embodiment, the width dimension of the current collecting tab is100 μm or more and 10 mm or less. When the width dimension is 100 μm ormore, the current collecting tab can have more excellent elasticity andrigidity. When the width dimension is 10 mm or less, the secondarybattery can be made more compact. In addition, the handling property ofthe current collecting tab can be further improved. The width dimensionof the current collecting tab is preferably 300 μm or more and 5 mm orless, for example, 500 μm or more and 2.5 mm or less.

In an embodiment, the thickness dimension of the current collecting tabis 10 μm or more and 3 mm or less.

When the thickness dimension is 10 μm or more, the current collectingtab can have more excellent elasticity and rigidity. When the thicknessdimension is 3 mm or less, the secondary battery can be made morecompact. In addition, the handling property of the current collectingtab can be further improved. The thickness dimension of the currentcollecting tab is preferably 50 μm or more and 2 mm or less, and is, forexample, 70 μm or more and 1 mm or less.

The parameters (that is, the length dimension, the width dimension, andthe thickness dimension) related to the shape of the current collectingtab may refer to a dimension measured using a micrometer (model numberMDH-25 MB manufactured by Mitsutoyo Corporation) or a height gauge, or avalue calculated from the dimension.

In an embodiment, the Young's modulus of the current collecting tab is50 GPa or more and 300 GPa or less. When the Young's modulus is withinsuch a range, the current collecting tab can have more excellentelasticity and rigidity while maintaining the good handling property.The Young's modulus of the current collecting tab is preferably 60 GPaor more and 250 GPa or less, and is, for example, 70 GPa or more and 200GPa or less.

The Young's modulus of the current collecting tab described above mayrefer to a value measured by a method conforming to JIS standard (JIS R1602). A tabletop precision universal tester (model number AGS-5kNXmanufactured by Shimadzu Corporation) may be used for measuring theYoung's modulus.

In an embodiment, the tensile strength of the current collecting tab is50 N/mm² or more and 1000 N/mm² or less. When the tensile strength iswithin such a range, it is possible to obtain a current collecting tabthat is more hardly broken while maintaining the good handling propertyof the current collecting tab. The tensile strength of the currentcollecting tab is preferably 80 N/mm² or more and 800 N/mm² or less, andfor example, 100 N/mm² or more and 600 N/mm² or less.

The tensile strength of the current collecting tab may refer to a valuemeasured by a method conforming to JIS standard (JIS Z 2241).

In an embodiment, the current collecting tab contains at least oneselected from the group consisting of stainless steel, aluminum, nickel,and copper. With such a configuration, it is possible to obtain thecurrent collecting tab with more excellent conductivity and elasticity.

The secondary battery according to the present disclosure can bemanufactured by a manufacturing method including the following steps.That is, a method of manufacturing a secondary battery according to thepresent disclosure includes a step (electrode assembling step) oflaminating or winding a positive electrode, a negative electrode, and aseparator disposed between the positive electrode and the negativeelectrode to obtain a precursor of an electrode assembly, and a step(housing step) of forming the current collecting tabs so as to form abent shape between the electrode assembly and a spacer while housing theelectrode assembly and the spacer in the exterior case, and injecting anelectrolyte into the exterior case.

In this step, as shown in FIG. 8, the positive electrode 1, the negativeelectrode 2, and the separator 3 having a rectangular shape are disposedin a predetermined order and laminated or wound to obtain a precursor ofthe electrode assembly. As shown in FIG. 9A, the precursor of theelectrode assembly may be the planar lamination type electrode assembly200 (see FIG. 1A) in which the positive electrode 1, the negativeelectrode 2, and the separator 3 are laminated in the thicknessdirection. Alternatively, as shown in FIG. 9B, the precursor of theelectrode assembly may be a wound electrode assembly 200 (see FIG. 1B)by winding the positive electrode 1, the negative electrode 2, and theseparator 3. Hereinafter, an assembly step of the wound electrodeassembly will be described.

First, the positive electrode 1 having the positive electrode currentcollecting tab 61 attached to one side of the positive electrode currentcollector 11, the negative electrode 2 having the negative electrodecurrent collecting tab 62 attached to one side of the negative electrodecurrent collector 21, and two rectangular separators 3 are disposed in apredetermined order and wound (see FIG. 9B). When a predeterminedtension is applied to the separator 3 at the time of winding, aprecursor of the electrode assembly in which the separator 3 convergestoward the winding axis P (or approaches each other) toward the distalend of the separator extension portion is obtained. The tension appliedto the separator 3 during winding is usually 0.1 N or more and 10 N orless, and preferably 0.5 N or more and 3.0 N or less from the viewpointof focusing.

The dimensions of the separator 3 to be used are not particularlylimited as long as a desired electrode assembly is obtained. Forexample, the length dimension w1 of the separator 3 in the widthdirection r is usually preferably 105% or more and 400% or less, and forexample, 120% or more and 200% or less the length of the positiveelectrode 1 or the negative electrode in the winding axis direction (seeFIG. 8). For example, the length dimension w2 of the separator 3 in thelongitudinal direction s may be appropriately determined according tothe dimension of the intended secondary battery (particularly, thenumber of windings for the electrode assembly).

After this step, the precursor of the wound electrode assembly may beformed into a substantially flat column shape by pressing the precursorin the diameter direction of the wound body as desired.

While the electrode assembly 200 and the spacer 4 obtained in theprevious step are housed in the exterior case 300, the currentcollecting tabs 61 and 62 are welded to the electrode terminal 5, andthe electrolyte is injected into the exterior case 300 through theinjection port 7 (see FIG. 2). Hereinafter, a case where the exteriorcase 300 includes an exterior case main body 310 and an exterior caselid 320, and an electrode terminal 5 and an electrode terminal structure5′ are provided on one face of the exterior case 300 will be describedin detail.

First, as illustrated in FIGS. 4 and 5, the current collecting tab 6(that is, the positive electrode current collecting tab 61 and thenegative electrode current collecting tab 62) is temporarily bent inadvance and adjusted so that the current collecting tab 6 has a portionK₁ having a bent shape bent from the spacer 4 toward the electrodeassembly 200 and a portion K₂ having a bent shape bent from theelectrode assembly 200 toward the spacer 4, and then the currentcollecting tab 6 straddles the spacer 4.

Next, the electrode assembly 200 and the spacer 4 are housed in theexterior case main body 310 (see FIG. 2). At this time, an adhesivelayer (not shown) provided on the main face of the spacer 4 toward theexterior case 300 is attached to the rivet portion 50 of the electrodeterminal structure 5′ (see FIG. 7). One end, of the positive electrodecurrent collecting tab 61, extending toward the exterior case 300 iswelded to the inner terminal 51 of the electrode terminal structure 5′(that is, the positive electrode terminal 51) (see FIG. 4). Similarly,one end, of the negative electrode current collecting tab 62, extendingtoward the exterior case 300 is welded to a position, of the inside ofthe exterior case 300, corresponding to the negative electrode terminal52 (see FIG. 5).

Next, the exterior case main body 310 and the exterior case lid 320 arewelded to each other (see FIG. 2). Finally, an electrolyte may beinjected from the injection port 7, and the injection port 7 may beclosed with a sealing plug (not shown). The welding may be achieved byany method known in the field of secondary batteries, and for example, alaser irradiation method may be used.

Although the embodiments of the present disclosure have been describedabove, only typical examples have been illustrated. A person skilled inthe art can easily understand that the present disclosure is not limitedthereto, and various embodiments are conceivable without changing thegist of the present disclosure.

The secondary battery according to the present disclosure can be used invarious fields in which electricity storage is expected. By way ofexample only, the secondary battery can be used in the fields ofelectricity, information, and communication in which anelectric/electronic device, and the like are used (for example,electric/electronic device fields or mobile device fields includingmobile phones, smartphones, notebook computers and digital cameras,activity meters, arm computers, electronic paper, RFID tags, card-typeelectronic money, small electronic machines such as smartwatches, andthe like), home and small industrial applications (for example, fieldsof electric power tools, golf carts, and home, nursing, and industrialrobots), large industrial applications (for example, fields offorklifts, elevators, and harbor cranes), transportation system fields(For example, fields of hybrid vehicles, electric vehicles, buses,trains, power-assisted bicycles, electric two-wheeled vehicles, and thelike), power grid applications (for example, fields such as varioustypes of power generation, road conditioners, smart grids, and householdpower storage systems), medical applications (medical equipment fieldssuch as earphone hearing aids), pharmaceutical applications (fields suchas dosage management systems), IoT fields, space and deep seaapplications (for example, fields of space probes and submersibles), andthe like.

The secondary battery according to the present disclosure can prevent ashort circuit that may occur particularly when an impact or heat isapplied to the battery. Therefore, the secondary battery according tothe present disclosure can be particularly preferably used for a mobiledevice application in which shock or heat can be applied from alldirections.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

1. A secondary battery comprising an electrode assembly including apositive electrode, a negative electrode, and a separator disposedbetween the positive electrode and the negative electrode, and anelectrolyte enclosed in an exterior case, wherein the secondary batteryincludes a spacer positioned between the electrode assembly and theexterior case, wherein the electrode assembly includes currentcollecting tabs of a positive electrode and a negative electrode eachprotruding from a same end face of the electrode assembly, wherein thespacer is positioned between an end face of the electrode assembly, fromwhich the current collecting tabs each protrude and an exterior case,and wherein at least one of the current collecting tabs of the positiveelectrode or the negative electrode has a bent shape between theelectrode assembly and the spacer.
 2. The secondary battery according toclaim 1, wherein the bent shape includes a bowed shape bent in an archshape.
 3. The secondary battery according to claim 1, wherein thecurrent collecting tabs extend to meander in sectional view in aseparation space between the electrode assembly and the spacer.
 4. Thesecondary battery according to claim 1, wherein a portion having thebent shape of the current collecting tab is in contact with the spacer.5. The secondary battery according to claim 1, wherein the currentcollecting tabs extend from a face, of the spacer, toward the electrodeassembly to a face, of the spacer, toward the exterior case to straddleopposing faces of the main face of the spacer.
 6. The secondary batteryaccording to claim 5, wherein the current collecting tab extends to bein contact with the opposing faces of the main face of the spacer. 7.The secondary battery according to claim 1, wherein between theelectrode assembly and the spacer, the current collecting tab is incontact with both the spacer and the separator.
 8. The secondary batteryaccording to claim 7, wherein at least two portions each having the bentshape of the current collecting tab are provided, and wherein one of thebent portions of the current collecting tab is in contact with thespacer, and wherein the other of the bent portions of the currentcollecting tab is in contact with the separator.
 9. The secondarybattery according to claim 1, wherein the electrode assembly has aseparator extension portion in which the separator extends outward ofthe positive electrode and the negative electrode at an end face fromwhich the current collecting tabs each protrude, and a portion havingthe bent shape of each of the current collecting tabs is in contact withthe separator extension portion.
 10. The secondary battery according toclaim 1, wherein the electrode assembly includes a wound electrodeassembly, and the positive electrode, the negative electrode, and theseparator are wound.
 11. The secondary battery according to claim 9,wherein the electrode assembly includes a wound electrode assembly, andthe positive electrode, the negative electrode, and the separator arewound.
 12. The secondary battery according to claim 11, wherein at leastpart of the separator extension portion has a bent shape convex towardan outer periphery of the wound electrode assembly.
 13. The secondarybattery according to claim 12, wherein the electrode assembly has aconvergence portion at which the separator extension portion converges,and a portion having the bent shape of the current collecting tab is incontact with the convergence portion.
 14. The secondary batteryaccording to claim 1, wherein an insulating material is provided atleast at a portion having the bent shape in each of the currentcollecting tabs.
 15. The secondary battery according to claim 1, whereinthe current collecting tab extends in a meandering manner while being incontact with the separator of the electrode assembly and the spacer in aseparation space between the electrode assembly and the spacer, andextends further outward beyond the spacer.
 16. The secondary batteryaccording to claim 15, wherein the exterior case further includes anelectrode terminal structure of one of a positive electrode terminal anda negative electrode terminal, and part of each of the currentcollecting tabs is positioned between the spacer and the electrodeterminal structure.
 17. The secondary battery according to claim 16,wherein the exterior case is a conductive case type exterior case, andassumes a charge whose polarity is opposite to a polarity of theelectrode terminal structure.
 18. The secondary battery according toclaim 1, wherein the positive electrode and the negative electrode arecapable of absorbing and releasing lithium ions.
 19. The secondarybattery according to claim 1, wherein the secondary battery is includedin a mobile device.